1. Field of the invention
The present invention relates to a device for separating particles which are conveyed in suspension in a gaseous flow which is kept moving by a negative-pressure generator unit. More in particular, the field of the present invention relates to a centrifugal separator which has a duct for loading the particles conveyed in suspension in the gaseous flow, a duct for discharging the separated particles and a duct for discharging the separated gaseous flow. Said duct for discharging the separated gaseous flow is connected to the negative-pressure generator unit. In particular, the power which allows the movement of the gaseous flow is generated by said negative-pressure generator unit. The field of the invention furthermore comprises valve means suitable to adjust the width of the passage of the gaseous flow; the adjustment of said width allows to adjust the load losses encountered by said gaseous flow in its motion, so as to adapt the device to different operating conditions and in particular to different amounts of particles conveyed in suspension.
The invention furthermore comprises an apparatus for the pneumatic conveyance of granular materials which comprises the above described device. In particular, said apparatus comprises a plurality of lines arranged in parallel; a separator device is arranged at the top of each line, and the discharge ducts of said separator device are all connected to a single negative-pressure generator unit.
More in particular, the field of the present invention relates to a particle separator device and to an apparatus for the pneumatic conveyance of granular materials which are applied to the conveyance of particles of material generated by processes for rinding cereals.
The above is in summary the main field of industrial utilization of the invention; said field, however, does not constitute a limitation of the scope thereof, since the device and the apparatus according to the invention, in particular as described and claimed hereafter, can be advantageously employed in any other equivalent field in which operations of conveying granular material and of separating a gaseous flow from the particles contained in suspension in said flow are performed.
In general, the field of the invention relates to devices and apparata which can automatically adjust the width of the passage of the gaseous flow, so as to automatically adapt to various operating conditions, and in particular so as to adapt to operating conditions in which the amounts of suspended particles are very different. An increase in the amount of suspended particles in fact tends to decrease the flow-rate of the gaseous flow and therefore the overall efficiency of the separation. On the contrary, a decrease in the content of suspended material tends to increase the flow-rate of the gaseous flow, also to the detriment of other pneumatic lines possibly arranged in parallel.
The field of the present invention therefore relates to a separator device and to a pneumatic conveyance apparatus which are capable of self-adjusting automatically according to the different amounts of suspended particles, so as to keep the actual flow-rates of the gaseous flow as constant as possible and close to the design values.
2. Prior Art
Devices and apparata of this kind are known and are described for example by the European patent No. 0036219, wherein a pressure sensor arranged on the centrifugal separator's loading duct controls a lever system and then a pneumatic valve so as to adjust, by means of a second valve, the width of the passage of the gaseous flow.
Said known devices and apparata however, entail some problems; first of all, they require every centrifugal separator to be served by pneumatic lines for the operation of said valves. A pressure sensor is furthermore required which must be sensitive even to very modest pressure changes. In practice there is a servo-assisted diaphragm sensor equipped with lever systems, which in turn actuates another diaphragm. It is therefore a complicated and expensive system which requires difficult adjustment and continuous maintenance.
Apparata are known in which each centrifugal separator is provided with means for measuring the airspeed which are adapted to transmit the data to a computer which evaluates, in a preset sequence, the condition of each conveyor unit and adjusts valves arranged on the air intake pipe.
However, these devices, too, entail problems. Even in this case, in fact, it is necessary to provide pneumatic or electric control lines; the system itself is complicated and expensive, especially if it is applied to a limited number of conveyance units. Delicate operations are furthermore required for the installation, programming and maintenance of the system. This system would seem to be more suitable for use with extremely numerous conveyor units, when a very large number of centrifugal separators is required, but in this case, since the adjustment of each centrifugal separator is performed sequentially, computing times tend to be too long, so that the system is not flexible enough in responding to sudden variations in the amount of suspended particles, and imbalances in the flow-rates thus arise.